Thermal Concept

 CONCEPTS OF THE ORIGIN OF MONSOON

Thermal Concept

It was Halley who propounded the thermal concept of the origin of the origin of Asiatic monsoon in a memoir presented to the Royal Society in 1686. This Theory was, however, applied to all continental regions besides Asia. According to it, the monsoon are considered to be gigantic convectional systems produced by differential seasonal heating of continental and oceanic areas. Monsoon are more than just seasonal winds and are also directly thermally induced. Thus, the origin of Asiatic monsoon may be ascribed to the thermal differences between land and sea.


During winter the huge landmass of Asian cools more rapidly than the surrounding oceans with the result that a strong high-pressure center develops over the continent. On the other hand, the pressure over adjacent oceans is relatively lower. As a consequence the pressure gradient is directed from land to sea . Therefor there is as outflow of air from the continental landmass towards the adjacent oceans so that it brings cold, dry air towards the low latitudes.

In summer the temperature and pressure condition are reversed. The huge lndmass og asia heats quickly and develops a strong low pressure centre . Moreover, the poleward shift of the Intertropical  Convergence Zone to a position over southern asia reinforces the thermally induced low pressure centre .The pressure over the  adjacent oceans being high , a sea-to-land pressure gradient is astablished. the surface air flow is, therefore, from the highs over the oceans towards the lows over the heated land. The air that is attracted into the centres of low pressure from over the oceans is warm and moist . It may be mentioned here that tropical maritime air mass , that is unstable and full water vapour, cannor yield precipitation by itself. some other factors sich as atmospheric or iandfrom barrier ( mountains or plateaus) which make this unstable and mosit air rise are required to bring about rainfall.